Fix complex property editing in nuxeo-data-table

<dom-module id="nuxeo-pouet-edit-layout">
  <template>
    <style>
      *[role=widget] {
        padding: 5px;
      }
      nuxeo-data-table {
      	height: 800px;
      }
    </style>
 

    <nuxeo-data-table items="{{document.properties.pouet:contacts}}" orderable="true" editable="true" role="widget">
      <nuxeo-data-table-column name="Name">
        <template>
          <div role="widget">[[item.name]]</div>
        </template>
      </nuxeo-data-table-column>

      <nuxeo-data-table-column name="Position">
        <template>
          <div role="widget">[[item.position]]</div>
        </template>
      </nuxeo-data-table-column>

      <nuxeo-data-table-column name="Role">
        <template>
          <nuxeo-directory-suggestion role="widget" value="[[item.role]]" label="Role" readonly="true" directory-name="role"></nuxeo-directory-suggestion>
        </template>
      </nuxeo-data-table-column>

      <nuxeo-data-table-column name="Expiry Date">
        <template>
          <div role="widget">[[item.expiryDate]]</div>
        </template>
      </nuxeo-data-table-column>

      <nuxeo-data-table-form>
        <template>
          <nuxeo-input value="{{item.name}}" label="Name" type="text"></nuxeo-input>
          <nuxeo-input value="{{item.position}}" label="Position" type="text"></nuxeo-input>
          <nuxeo-directory-suggestion value="{{item.role}}" label="Role" directory-name="role"></nuxeo-directory-suggestion>
          <nuxeo-input value="{{item.expiryDate}}" label="Expiry Date" type="text"></nuxeo-input>
        </template>
      </nuxeo-data-table-form>
    </nuxeo-data-table>

  </template>

  <script>
  Polymer({
    is: 'nuxeo-pouet-edit-layout',
    behaviors: [Nuxeo.LayoutBehavior],
    properties: {

      /**
         * @doctype Record
         */
      document: {
        type: Object,
      },

    }
  });
  </script>
</dom-module>

Uncaught (in promise) RangeError: Maximum call stack size exceeded
    at extend (elements.html:8527)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)
    at extend (elements.html:15403)